We're hearing more reaction from Ontario Premier Doug Ford, who has been speaking to US network CNBC.

Ford says he'll be speaking to US Commerce Secretary Howard Lutnick "sometime today", and emphasises that the neighbouring countries "need to sit down at the table" and resolve their differences.

The Ontario leader has threatened to cut off electricity exports to the US in full if Trump escalates the trade war, but he says this is "the last thing" he wants to do.

But, he says if both countries do slide into a recession as a result, "it will be called the Trump recession".

Earlier on, Ford told MSNBC that he "will be relentless" in responding to any new tariffs introduced by the US president.

Today's tariff escalation isn't the first time that Canadians have had to deal with fears about costs going up as a result of Donald Trump's trade policies.

Since the US president first threatened tariffs of 25% on Canadian goods in November, stores in the country have started to swap out American products for local ones.

In some regions, "Choose Canadian" stickers adorn the shelves where American goods typically sit.

And, Canadian citizens have had their say on how they'll change their habits - you can see their reaction in the video at the top of this post.

Bernd Debusmann Jr
Reporting from the White House

Speaking at her morning news conference in Mexico City, President Claudia Sheinbaum took a question on whether she believed that her country would ultimately receive similar tariffs as Canada from the US and the Trump administration.

"No," she responded curtly. "We're respectful."

She added that Mexico's Secretary of the Economy, former Mexico City mayor and Foreign Minister Marcelo Ebrard, would meet with her tomorrow to discuss the issue.

Brandon Drenon
Reporting from Washington DC

Trump's tariffs are likely to push up prices on everyday items for US consumers, said John Rogers, an economics professor at American International University.

"Prices could go up pretty soon," Rogers warned, though he was reluctant to say by exactly how much or how quickly.

"We are in pretty uncharted territory," he told the BBC.

Steel and aluminium, "those go into all kinds of other products", Rogers said.

"So you protect the US steel industry, but you wind up paying more for steel.

"That's going to affect the price of anything that has steel in it - your automobiles, your dishwashers and other appliances, your construction."

For Rogers, it was hard to see any upside of a US-Canada trade war.

"Everybody's just going to wind up paying higher prices, sacrificing quality, even the American manufacturers, who are going to be presumably the beneficiaries," he said.

Bernd Debusmann Jr
Reporting from the White House

Speaking at the White House earlier this morning, US Secretary of Agriculture Brook Rollins said she believed the US economy would be a "little bumpy" in the short-term, although she expressed confidence in the future.

Following an interview with Fox, Rollins spoke to reporters and acknowledged that "uncertainty is real" for American farmers amid the tariffs.

"The farmers and our ranchers are concerned," she said.

While Rollins said that tariffs are and will remain an important part of the president's "toolkit", she said the administration continues to "have our ag producer's back, and the farmers and the ranchers."

"He's been very clear, it's going to be a little bumpy for a few weeks, or a few months," she said.

"But at the end, his vision... is that our American farmers and ranchers, but truly all Americans, will be moving into an era of greater prosperity."

Natalie Sherman
New York business reporter

This new escalation is the kind of abrupt policy change that has raised alarm among many US businesses.

Jason Goldstein is founder of Icarus Brewing, a small beer-maker in New Jersey that employs 50 people. He says Trump’s tariff announcements have prompted a slew of emails from his suppliers, warning that price increases for everything from grain and aluminium cans are likely to be coming.

He has stockpiled an extra month’s supply of cans and held off on new purchases, as a result of the uncertainty and rapidly changing situation..

“It’s definitely a worrying time for us,” he told the BBC on Monday, a day before the latest announcement.

“Never before in my life have I had to read so much news, watch so much news to know, he’s what’s my industry going to look like tomorrow.”

Nadine Yousif
Reporting from Toronto

Yves-Francois Blanchet, leader of the Bloc Quebecois - a political party in Canada - has just spoken about the latest Trump tariff news.

"It seems to be the proof of his failure. If he believed 25% were hard enough on us to have us bend the knee, he would be satisfied with that," Blanchet says.

"But now it's 50% on aluminium and steel.

"He uses some Quebec interests to avenge himself against Ontario, which is weird ... He doesn't have much time before his own economy, inflation and markets, show him that this has already lasted long enough, and that he's got to sit at the table and start a serious negotiation."

More now from US President Donald Trump, who has just posted again on Truth Social.

He is talking about Monday's announcement from Ottawa Premier Doug Ford, who will implement a surcharge on electricity exports to the US in retaliation to Trump's tariffs on Canada.

Trump writes: "Why would our Country allow another Country to supply us with electricity, even for a small area?"

"Can you imagine Canada stooping so low as to use ELECTRICITY, that so affects the life of innocent people, as a bargaining chip and threat?

"They will pay a financial price for this so big that it will be read about in History Books for many years to come!"

• As a reminder: About an hour ago, Trump said he will raise tariffs on Canadian steel and aluminium to 50% from Wednesday, saying this was "based on Ontario, Canada, placing a 25% tariff on electricity" coming into the US.

The US imports more steel than any other country - and Canada, Brazil and Mexico are its top three suppliers.

Trump has said Canada will be hit with 50% tariffs on steel and aluminium. That will start on Wednesday.

Canada is also the largest supplier of aluminum to the US, providing almost 60% of the amount imported.

American companies that use steel and aluminium to make products have warned the tariffs could push prices up.

During his first term as president, Trump previously announced tariffs of 25% on steel and 10% on aluminium in 2018 - but made exceptions to exclude Canada and Mexico.

Still, despite those previous exemptions, tariffs raised the average price of steel and aluminium in the US by 2.4% and 1.6% respectively, according to the US International Trade Commission.

Bernd Debusmann Jr
Reporting from the White House

Image source, Bernd Debusmann Jr/BBC

It's an extremely quiet day so far at the White House, with only a small handful of reporters and staff members on the property at the moment.

In a few hours, at 13:00 EST (17:00 GMT), White House Press Secretary Karoline Leavitt is due to hold a press briefing. Tariffs are almost certainly top of the agenda, alongside foreign policy issues such as the Ukraine-Russia talks.

Later, Trump will host a meeting of business leaders at a roundtable in Washington DC.

We've not seen the President in front of the cameras since Sunday night, when he addressed reporters on-board Air Force One. His absence is a rarity during this administration. More often than not, he is seen by reporters at least once on any given day.

Cabinet members and political allies have, however, been making the rounds of US media to defend Trump's handling of the economy, which has dominated the headlines amid a slump in the stock market.

We've just heard from Doug Ford, premier of Canada's most populous province Ontario. He was speaking on MSNBC when Trump said he would be doubling steel and aluminium tariffs.

On Monday, Ford announced his own tariffs in response to US President Donald Trump's tariffs against Canada. Ford announced a 25% surcharge on electricity exports that will affect 1.5 million homes and businesses across Minnesota, Michigan and New York.

Today, Ford says he loves Americans but "we will not back down" and "we will be relentless", claiming Trump has unleashed an "unprovoked attack" on Canada.

Ford says he will respond "appropriately" on the electricity surcharge, telling viewers to "stay tuned".

Ford then urges Trump to "stop the chaos", saying it is hurting American and Canadian families.

When Ford announced electricity surcharges for the US on Monday, he warned that if things escalated he "will not hesitate to shut off electricity completely".

Brandon Drenon
Reporting from Washington DC

Yesterday I attended a conference in Washington DC where I bumped into Tim Tierney, a city councillor from Ottawa, Canada.

Tierney told me he was "very concerned" about the prospect of a trade war between the US and Canada - "two very good friends for a very long time".

Tariffs are "a punishment to residents on both sides of the border", he said, mentioning that the current tariffs were "upsetting the markets on both sides".

"We're hoping cooler heads prevail," Tierney said.

If they don't, Tierney said, Canadians are prepared to be "elbows up" (a hockey reference meaning prepared to fight).

He rolled up his sleeve to show me a new tattoo of a maple leaf on his forearm, a reflection of the renewed pride he said most Canadians are now feeling.

"We will never be the 51st state (in the US). We are our own nation. We're very proud Canadians," he said.

"We respect our American friends, but we won't be bullied."

In his lengthy social media post, Trump again raises his desire for Canada to become the 51st US state.

Since returning for his second term as president, Trump has frequently suggested that he wants Canada to join America’s other 50 states and become part of the US.

Today, he writes: "We are subsidizing Canada to the tune of more than 200 Billion Dollars a year. WHY??? This cannot continue. The only thing that makes sense is for Canada to become our cherished Fifty First State."

The US president says such a move would make all tariffs "disappear", would make Canadians more secure and reduce taxes in the country.

He goes on to say that it would make the "greatest and most powerful nation" even "bigger, better and stronger" and erase the "artificial line" separating the two nations.

Canadians have consistently rejected the suggestion of joining the US.

Last week, Foreign Minister Mélanie Joly told BBC Newsnight that she takes Trump’s remarks “very seriously”.

And, incoming prime minister Mark Carney responded to threats of annexation, during his victory speech, saying: “Canada will never be part of America”.

Image source, Getty Images

In a Sunday television interview, Donald Trump was asked about the possibility of the US entering a recession. His response was the world's biggest economy was in a "period of transition".

The comments triggered a significant sell-off in the US stock market on Monday. The S&P 500, which tracks the biggest American companies, fell about 2.7% - its worst day this year.

The tech-heavy Nasdaq was hit even harder, falling roughly 4%. Elon Musk's Tesla was hit hard, dropping 15.4%.

On Tuesday morning, US markets opened modestly lower, but has not had the deep plunges it experienced yesterday. The S&P is down about 1%, and the Nasdaq is down 0.8%.

The latest plunge follows a downward stock market trend that began last week as Trump's initial tariffs against Canada and Mexico took hold.

Tariffs are a central part of Trump's economic plans. He says tariffs will boost US manufacturing and protect jobs, as well as raising tax revenue and growing the economy.

Goods from China, Mexico and Canada accounted for more than 40% of imports into the US in 2024.

But Trump has accused the three countries of not doing enough to end the flow of migrants and illegal drugs such as fentanyl into the US.

All three countries have rejected the accusations.

Fentanyl is linked to tens of thousands of overdose deaths in the US each year.

Outgoing Canadian Prime Minister Justin Trudeau said his country was responsible for less than 1% of fentanyl entering the US, most of which comes from Mexico.

More now on Trump's latest comments, where he says he will be raising tariffs on all steel and aluminium coming into the US from Canada by 50%.

He says the move will come into effect tomorrow morning, and is in response to the Canadian government introducing a 25% tariff on electricity exports to the US.

Trump writes on social media: "I will shortly be declaring a National Emergency on Electricity within the threatened area. This will allow the U.S to quickly do what has to be done to alleviate this abusive threat from Canada.

"If other egregious, long time Tariffs are not likewise dropped by Canada, I will substantially increase, on April 2nd, the Tariffs on Cars coming into the U.S. which will, essentially, permanently shut down the automobile manufacturing business in Canada."

Trump's post on Truth Social says: "Based on Ontario, Canada, placing a 25% Tariff on 'Electricity' coming into the United States, I have instructed my Secretary of Commerce to add an ADDITIONAL 25% Tariff."

Yesterday, Ontario's Premier Doug Ford announced a 25% surcharge on US-bound electricity.

Roughly 1.5 million American homes and businesses in the northern border states of New York, Michigan and Minnesota will be impacted.

"President Trump's tariffs are a disaster for the U.S. economy. They're making life more expensive for American families and businesses," Ford said in a statement on Monday.

At Monday's news conference, Ford threatened to escalate further if the US increases their tariffs on Canada.

"I will not hesitate to increase this charge if necessary," he said. "If the US escalates, I will not hesitate to shut off electricity completely."

Brandon Livesay
Reporting from New York

Hello and welcome to our live coverage of US politics.

US President Donald Trump has just shared on social media that he will be raising the tariff on all steel and aluminium coming into the US from Canada to 50%.

A 25% tariff was set to be implemented on Wednesday.

Stick with us, more to come.